Meso Fracture Characteristics Of Deep Granite And Local Instability Evolution Law Of Surrounding Rock

Rocks in nature are affected by long-term geological structures and complex physical and geological environments,and have complex features such as heterogeneity and discontinuity.Rock mechanical behavior is controlled by microstructure,while complex macroscopic behaviors such as cracks are caused by the interaction of microstructure.Discrete element method is usually used in the calculation and analysis of geotechnical engineering to analyze the complex mechanical properties of rock.A numerical calculation model which can characterize the mechanical properties of different types of rock is proposed,and the numerical method of constructing large-scale refined model is realized.It is very important to deeply study the meso fracture characteristics of rock mass and analyze the macro fracture law of deep chamber surrounding rock.In this paper,the uniaxial compressive strength test and the Brazilian disc splitting test of complete and fractured granite samples are used to study the strength variation law of the samples with different cracks,and the meso-fracture characteristics and crack propagation law of the samples are analyzed.Based on particle flow theory,the construction method of variable radius proportional Clump model is proposed,and the influence rules of meso-structure and mesoparameters on the tensile and compression characteristics of simulated rock samples are analyzed.A numerical calculation model of deep cavern with gradual particle density is established using the variable radius ratio Clump model construction method,and the macroscopic fracture law of the surrounding rock of deep enclosed cavern is analyzed.The research results are as follows:(1)Uniaxial compressive strength test and Brazilian disc splitting test on complete and fractured granite samples are performed to obtain stress-strain curves.Mechanical parameters such as uniaxial compressive strength,tensile strength,peak strain and elastic modulus are obtained.The strength variation law and crack propagation law of different fractured samples are studied to obtain meso-fracture properties of complete and fractured granite samples.(2)Based on the particle flow theory,a Clump structure modeling method with variable radius scale suitable for rock materials is proposed,and the influence of meso mechanical parameters on tension and compression properties of the model is analyzed.A granite numerical model is constructed and the parameters are calibrated after sensitivity analysis of meso parameters.It is known that the laboratory test results are in good agreement with the numerical simulation results by numerical calculation and verification,providing a reference for studying the mesofracture properties of rock materials.(3)According to the Clump structure modeling method with variable radius scale and the calibrated model parameters,the deep cavern numerical model with gradual particle density and high stress is constructed.The evolution of stress field and micro fracture field in roadway surrounding rock and the range and shape of fracture zone after excavation are studied.Compared with practical engineering,and the local instability law of cavern surrounding rock under high stress condition is studied.The results show that the model can practically reflect the failure properties of the surrounding rock in high stress cavern and can provide reference for similar deep mining engineering research.